Seal-less reusable vacuum bag

ABSTRACT

A reusable vacuum bag is configured for application of at least one sealant bead for providing vacuum tight sealing of the reusable vacuum bag to a forming tool during fabrication of a composite part. The reusable vacuum bag comprises at least one elastomeric layer and a fluoroelastomeric strip. The elastomeric layer is sealable to the forming tool and has a sealing flange extending peripherally thereabout. The fluoroelastomeric strip extends substantially along the sealing flange and has first and second surfaces. The elastomeric layer and the fluoroelastomeric strip each have polymers and a peroxide curative. The peroxide curative initiates vulcanization wherein the polymers of each material cross-link at an elevated temperature to form double-oxygen bonds such that a permanent bond is formed between the sealing flange and the fluoroelastomeric strip at the first surface. The fluoroelastomeric strip is releaseably adhered at the second surface to the sealant bead.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] (Not Applicable)

STATEMENT RE: FEDERALLY SPONSORED RESEARCH/DEVELOPMENT

[0002] (Not Applicable)

BACKGROUND OF THE INVENTION

[0003] The present invention relates generally to vacuum bags and, moreparticularly, to an improved reusable vacuum bag configured forapplication of at least one sealant bead for sealing the reusable vacuumbag to a forming tool during fabrication of a composite part on theforming tool.

[0004] The production of composite parts requires the application ofpressure onto a composite part against a forming tool. The vacuum bag isused for debulking the composite part such that wrinkles and trapped airin the composite part may be forced out under vacuum pressure. Thevacuum bag is also utilized to hold the composite part against theforming, tool while uncured resin is impregnated therein by vacuumpressure. The vacuum bag is further used for curing the resin in thecomposite part in an autoclave or in an oven at elevated temperature andpressure. After curing, the composite part is returned to roomtemperature. The vacuum bag is then removed from the forming tool sothat the composite part may be separated from the forming tool.

[0005] Because the construction of vacuum bans is time-consuming,expensive, and requires skilled personnel, it is desirable that thevacuum bag be reusable. A common vacuum bag material is nylon. Forfabricating composite parts on a forming tool having small inside andoutside radii, nylon vacuum bags are desirable as the thin nylon filmcan be laid over the composite part on the forming tool. The nylon filmcan then be hand conformed to the small inside radii of the formingtool. However, nylon loses considerable resiliency after a single use inan autoclave and therefore cannot be reused to fabricate anothercomposite part. Furthermore, composite parts fabricated using nylonvacuum bags may exhibit flaws in that wrinkles and pinholes may appeardue to the bunching up of the nylon film against the forming tool undervacuum pressure. Leakage of the seal between the vacuum bage and theforming tool has also limited production of composite from nylon vacuumbags. As an alternative, silicone rubber has been utilized to fabricatevacuum bags because it has an elongation of over 500% which allows it tostretch over small radii on forming tools. Furthermore, silicone rubberhas a maximum exposure temperature of 500° F. which allows for greatercuring cycle flexibility. Finally, as compared to nylon, silicone rubberretains its resiliency over many autoclave cycles and is thereforesuitable as a reusable vacuum bag material.

[0006] Importantly, the seal between the vacuum bag and the forming toolis critical in the quality of the resulting composite part as any lossof uniform vacuum pressure adversely affects the quality of the curedpart. Common sealing techniques include the use of clamps located at thebag border. However, their use is cumbersome and the seal is not alwaysreliable. Magnets may also be spaced around the bag border. However,magnets are only practical for use with relatively flat steel formingtools, and are not useful in border areas on non-steel tools. Mechanicalseals such as channels, grooves and keys formed in the base plate of theforming tool may work reasonably well for composite parts withrelatively large curvatures. However, for forming tools having smallinside and outside radii, mechanical seals cannot be used. Commercialsealant tapes may be used to seal the vacuum bag to the forming tool dueto their hand-moldable, highly conformable, putty-like consistency. Zincchromate sealant tape is one such sealant tape that is widely used incomposite part manufacturing. Zinc chromate sealant tape is not limitedby the material of the forming tool as it adheres to both metallic andcomposite forming tools.

[0007] However, a principal limitation in the use of silicone rubber forreusable vacuum bags is that standard sealant tapes do not readilyadhere to silicone rubber due to the inherently natural lubricity ofsilicone. Although commercial sealants, including zinc chromate sealanttape, adhere to and cleanly remove from metal or composite forming toolsafter use, these commercial sealants do not adhere to silicone rubber.Attempts have failed at combining the reusable characteristics of asilicone rubber vacuum bar with a commercially available vacuum bagsealant and, more particularly, to improve the adhesion of commercialsealant to a silicone rubber vacuum bag.

[0008] Another limitation in the use of silicone rubber is that it issubject to chemical attack by tacifiers in sealant tapes. A reusablevacuum bag must be resistant to attack and degradations from acids,caustics, and tacifiers such as those that may be found within the manycommercially available sealant tapes. Unfortunately, silicone rubber ishighly susceptible to chemical attack from tacifiers in these sealanttapes. Reusable vacuum bags formed of silicone rubber may lose theirmechanical strength and tear resistance due to exposure to tacifiersemanating from compounds in the sealant tape. Although initially hard,the compounds soften at the elevated temperatures typical of autoclavesand ovens. The softening compounds form into tacifiers that attacksilicone rubber and degrade the mechanical properties of the siliconerubber such that after two or three autoclave cycles, the bag must bediscarded.

[0009] The prior art discloses several reusable vacuum bags that arefabricated from silicone rubber. U.S. Pat. No. 4,842,670 (Callis et al.)entitled “MOLDED VACUUM BAG FOR DEBULKING AND AUTOCLAVING LAMINATES OFCOMPLEX SHAPES” describes a silicone rubber vacuum bag assembly whichcan be used repeatedly to debulk and autoclave composite layups. Thebags are formed of a single layup of uncured silicone rubber over aforming tool. Portions of the bag which may overlay recesses and femaleradii are removed. The silicone rubber is vacuum bagged in a nylon bagand cured in an autoclave. The recesses are then filled with uncuredsilicone rubber followed by a second cure period. After removal of thenylon bag from the forming tool, each of the vacuum bag assemblies ispostcured to stabilize and preshrink the silicone rubber. The vacuum bagassembly may be bonded to a frame for sealing to the forming tool.Although the resulting silicone rubber vacuum bag is reusable andexhibits good conformability, the added complexity of a frame mayincrease the cost of such a vacuum bag. Furthermore, the addition of aframe eliminates the ability to use the vacuum bag on some complexshapes.

[0010] U.S. Pat. No. 4,698,115 (Dodds) entitled “SILICONE RUBBER VACUUMBAG TOOL AND METHOD OF FABRICATING SAME” describes a reusable vacuumbate tool utilizing a silicone rubber sheet as the bag material whereinedges of the bag are prepared so that a commercially available sealanttape may be used to seal the vacuum bag to a forming tool. The siliconerubber sheet has strips of silicone elastomeric material adhered to theedges. The strips are cured to the surface of the sheet along the edges.To seal the reusable vacuum bag to a base plate of the forming tool, astrip of adhesive tape, commercially available as Mosites #14206 fromthe Mosites Rubber Company, is adhered to each strip of siliconeelastomeric material. Although the silicone vacuum bag described in thereference is reusable, the Mosites sealant tape would not be applicablefor use on complex contoured forming because wrinkling of the tape willoccur when applied to small radii, resulting in leakage during vacuumpull

[0011] Thus, there exists a need in the art for a reusable vacuum bagfor forming composite parts having small radii of curvature.Additionally, there exists a need for a reusable vacuum bag that can beeffectively sealed to a forming tool to hold a vacuum duringautoclaving. Finally, there exists a need for a reusable vacuum bag towhich commercially available sealant tape may be adhered and which hashigher resistance to tears during use.

BRIEF SUMMARY OF THE INVENTION

[0012] The present invention specifically addresses and alleviates theabove referenced deficiencies associated with the sealing of reusablevacuum bags to a forming tool. More particularly, the present inventionis an improved border configuration for sealing a reusable vacuum bag toa forming tool and a method of fabricating the reusable vacuum bag. Aswill be demonstrated below, the reusable vacuum bag of the presentinvention differs from reusable vacuum bags of the prior art in that itutilizes a fluoroelastomeric strip for sealing the reusable vacuum bagto the forming tool with commercially available sealant tape. Inaddition, the reusable vacuum bag of the present invention providesimproved tack and adhesion to sealant tape, thus allowing for a vacuumtight seal to the forming tool. Finally, the combination of thefluoroelastomeric strip with silicone rubber provides a reusable vacuumbag with improved mechanical properties capable of withstanding the wearand tear of multiple manufacturing cycles.

[0013] In accordance with the present invention, there is provided areusable vacuum bag that is configured for the application of a sealantbead for vacuum tight sealing, of the reusable vacuum bag to a formingtool. The forming tool has a contoured surface incorporating the desiredshape of the composite part to be formed. The forming tool perimeter maybe a generally flat or contoured surface to which the reusable vacuumbag is sealed for debulking or autoclaving operations.

[0014] The reusable vacuum bag is comprised of at least one elastomericlayer and a fluoroelastomeric strip. The elastomeric layer may be formedof silicone rubber provided in either a cured or uncured state. Theelastomeric layer is sealable against the forming tool and transmitsautoclave pressure to the composite part when a vacuum is drawnthereagainst. The reusable vacuum bag may include a release layerdisposed on the surface of the composite part on the side opposite theforming tool to allow detaching of the composite part from the formingtool after autoclaving. The reusable vacuum bag may also include abreather layer disposed on the surface of the release layer on the sideopposite the composite part. The breather layer may have exposedinterstices for drawing a vacuum between the reusable vacuum bag and theforming tool and to allow passage of gas volatiles that may be generatedby the composite part as it cures during curing. The elastomeric layerhas a sealing flange extending peripherally thereabout. Thefluoroelastomeric strip extends substantially along the sealing flangeand has first and second surfaces. Although silicone does not adhere tosealant tapes and is subject to chemical attack from tacifiers in thesealant tape, it has been found that Mosites #10320-C. manufactured bythe Mosites Rubber Company of Fort Worth, Tex., is a fluorinatedsynthetic rubber which is chemically inert and which thus has excellentresistance to attack from sealant tape tacifiers with no substantialdegradation in its mechanical properties even after repeated contactwith tacifiers. The high resistance to attack from tacifiers is due inpart to its relatively high fluorine content of 70%. In addition,commercial sealant tapes readily adhere to Mosites #10320-C.

[0015] The elastomeric layer and the fluoroelastomeric strip may eachinclude polymers and a peroxide curative. The peroxide curativesinitiate vulcanization wherein the polymers of each material cross-linkat an elevated temperature to form double-oxygen bonds such that apermanent bond is formed between the sealing flange and thefluoroelastomeric strip at the first surface. Mosites #10320-C can bepermanently bonded to Mosites #10320-C due in part to the peroxidecurative contained within the #10320-C compound. The fluoroelastomericstrip is releaseably adhered at the second surface to the sealant bead.

[0016] The reusable vacuum bag may be fabricated by providing theelastomeric layer having a sealing flange, and covering the forming toolwith the elastomeric layer. A fluoroelastomeric strip is positionedbetween the sealing flange and the forming tool such that thefluoroelastomeric strip is substantially aligned along the sealingflange. The forming tool may be overlaid with a model part prior tocovering with the elastomeric layer to compensate for the thickness ofthe composite part. Such a model part would be preformed and would havethe same thickness and geometric features of the composite part. If thelaminate thickness is small and the lateral geometric features are nottoo large, the model part need not be incorporated into the process forfabricating the reusable vacuum bag. The reusable vacuum bag overlayingthe forming tool is then vacuum bagged with a nylon bag usingconventional bagging techniques. The reusable vacuum bag is then curedby placing in an autoclave or oven at elevated temperature and pressure.After curing, the nylon bag and the reusable vacuum bag, are removedfrom the forming tool. The reusable vacuum bag is stabilized bypostcuring in an oven at ambient pressure and elevated temperature inorder to minimize further shrinkage of the reusable vacuum bag.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] These as well as other features of the present invention willbecome more apparent upon reference to the drawings wherein:

[0018]FIG. 1 is a broken away perspective view of a composite partformed on a forming tool utilizing a reusable vacuum bag of the presentinvention;

[0019]FIG. 2 is an enlarged partial longitudinal sectional view takenalong line 2-2 of FIG. 1 illustrating the arrangement of the layers thatmake up the reusable vacuum bag of the present invention;

[0020]FIG. 3 is an enlarged longitudinal sectional view taken from FIG.2 illustrating the detail of the sealing flange and the arrangement of asealant bead with the forming tool;

[0021]FIG. 4 is an enlarged longitudinal sectional view of a reusablevacuum bag of the prior art illustrating the arrangement of the sealingflange with the sealant bead;

[0022]FIG. 5 is a broken away perspective view of the forming tool andthe reusable vacuum bag during fabrication thereof and

[0023]FIG. 6 is an enlarged partial longitudinal sectional view takenalong line 6-6 of FIG. 5 illustrating the detail of the sealing flangeduring fabrication of the reusable vacuum bag.

DETAILED DESCRIPTION OF THE INVENTION

[0024] The present invention will now be described in particular withreference to the accompanying drawings.

[0025]FIG. 1 illustrates a composite part 18 formed on a forming tool 16utilizing a reusable vacuum bag 10 of the present invention. In FIG. 1,the forming tool 16 is shown having a contoured surface incorporatingthe desired shape of the composite part 18 to be formed. The formingtool 16 perimeter may be a flat or a contoured surface to which thereusable vacuum bag 10 is sealed during preparation of the compositepart 18, shown in FIG. 1, for debulking or curing. Composite part 18material is typically comprised of sheets or plies of woven orunidirectional filamentary material. The plies are laid over the formingtool 16. The plies are generally pre-impregnated with resin and are thenplaced on the forming tool 16. A vacuum pressure is drawn on the pliesand the forming tool 16 with the aid of the reusable vacuum bag 10. Theentire assembly of the forming tool 16, the composite part 18 and thereusable vacuum bag 10 is then placed in an autoclave in which the layupis finally cured through the application of further pressure at anelevated temperature. After removal from the autoclave and cooling downto room temperature, the reusable vacuum bag 10 and the composite part18 are removed from the forming tool 16.

[0026] The reusable vacuum bag 10 of FIG. 1 is comprised of at least oneelastomeric layer 20 and a fluoroelastomeric strip 24. The elastomericlayer 20 is sealable to the forming tool 16. It is contemplated thatthere may be multiple elastomeric layers 20 that make up the reusablevacuum bag 10. The elastomeric layer 20 may be formed of silicone rubberwhich may be provided in either a cured or uncured state. Furthermore,it is contemplated that the silicone rubber ma have a thickness of fromabout 0.030 inches to about 0.120 inches, although the thickness of thesilicone rubber may be of a thickness outside such a range depending onother variables such as the relative radii of curvature in the formingtool 16 and the overall size of the forming tool 16. It is furthercontemplated that the elastomeric layer 20 may have variable thicknessesat different sections on the reusable vacuum bat 10. For example, insections where the reusable vacuum bag 10 traverses small male or femaleradii of the forming tool 16, the elastomeric layer 20 may be thinner toallow the reusable vacuum bag 10 to more readily stretch and conform thecomposite part 18 to the forming tool 16. In sections where the reusablevacuum bag 10 traverses broad, relatively flat sections of the formingtool 16, the elastomeric layer 20 may be thicker. The elastomeric layer20 transmits autoclave pressure to the composite part 18 when a vacuumis drawn thereagainst. The reusable vacuum bag 10 is configured forapplication of at least one sealant bead 14, shown in FIGS. 1 and 2 anddescribed in more detail below.

[0027]FIG. 2 is an enlarged partial longitudinal sectional view takenalong line 2-2 of FIG. 1 illustrating the arrangement of the layers thatmake up the reusable vacuum bag 10. Although not necessary, the reusablevacuum bag 10 may further include at least one release layer 32, shownin FIG. 2, disposed on the surface of the composite part 18 on the sideopposite the forming tool 16. The release layer 32 may provide releaseproperties to the reusable vacuum bag 10 such that the reusable vacuumbag 10 is detachable from the composite part 18 after autoclaving. Therelease layer 32 may be fluorinated ethylene propylene material or itmay be a TEFLON release film or a TEFLON coated fabric. The reusablevacuum bag 10 may also include a breather layer 34, also shown in FIG.2, disposed on the surface of the release layer 32 on the side oppositethe composite part 18. The breather layer 34 may have exposedinterstices 36 for drawing a vacuum between the reusable vacuum bag 10and the forming tool 16. Such interstices 36 may allow passage of gasvolatiles that may be generated by the composite part 18 as it curesduring autoclaving. Such gas volatiles must leave the surface of thecomposite part 18 during curing in order to produce a composite part 18of high quality. The breather lay 34 may be fabricated of a wovenmaterial. The breather layer 34 may also be fabricated from non-wovenpolyester or nylon fiber material.

[0028] Turning now to FIGS. 3 and 4, shown in both views is thearrangement of a sealing flange 22 of the reusable vacuum bat 10 withthe forming tool 16. FIG. 3 is an enlarged longitudinal sectional viewtaken from FIG. 2 illustrating the detail of the sealing flange 22 andthe arrangement of the sealant bead 14 with the forming tool 16. FIG. 4is an enlarged longitudinal sectional view of a reusable vacuum bag 10of the prior art illustrating the arrangement of the sealing flange 2with the sealant bead 14. The sealing flange 22, also shown in FIGS. 1and 2, extends peripherally about the elastomeric layer 20. It iscontemplated that the sealing flange 22 may have a width in a range offrom about {fraction (1/2)} inch to about 3 inches, although the widthof the sealing flange 22 may fall outside of this range. In contrast tovacuum bags of the prior art wherein the sealant bead 14 is disposedagainst the sealing flange 22 as shown in FIG. 4, the sealing flange 22of the present invention includes the fluoroelastomeric strip 24extending substantially along the sealing flange 22, as shown in FIG. 3.The sealant bead 14 is applied between the sealing flange 22 and thefluoroelastomeric strip 24 for sealing the fluoroelastomeric strip 24 tothe forming tool 16. Importantly, the sealant bead 14 provides vacuumtight sealing of the reusable vacuum bag 10 to the forming tool 16during debulking and autoclave curing, of the composite part 18. Thefluoroelastomeric strip 24 is also shown in FIG. 3 having first andsecond surfaces 26, 28 with the first surface 26 thereof disposedagainst the sealing flange 22. The elastomeric layer 20 and thefluoroelastomeric strip 24 each have polymers. The polymers of theelastomeric layer 20 cross-link with the polymers of thefluoroelastomeric strip 24 at an elevated temperature typical ofautoclaves and ovens. The cross-linking of the polymers may be such thata permanent bond is formed between the sealing flange 22 and thefluoroelastomeric strip 24 at the first surface 26. The elastomericlayer 20 and the fluoroelastomeric strip 24 may both include a peroxidecurative that initiates vulcanization of the fluoroelastomeric strip 24to the elastomeric layer 20 at an elevated temperature to form apermanent bond therebetween.

[0029] Also shown in FIGS. 3 and 4 is the sealant bead 14 disposedbetween the elastomeric layer 20 and the fluoroelastomeric strip 24. Thefluoroelastomeric strip 24 in FIG. 3 has a second surface 28 oppositethe first surface 26. The second surface 28 is releaseably adhered atthe second surface 28 to the sealant bead 14. It is contemplated thatthe sealant bead 14 may include tacifiers therein. The tacifiers mayprovide adhesion between the sealant bead 14 and the fluoroelastomericstrip 24. Advantageously, as opposed to silicone rubber,fluoroelastomeric material adheres to commercial sealant tapes.

[0030] Commercial sealant tapes such as zinc chromate sealant tape alsocontain vulcanizing curatives. The curatives in the sealant tape allowthe sealant bead 14 to vulcanize at an elevated temperature, resultingin cross-linking within the sealant tape material itself and subsequenthardening or thermosetting of the sealant bead 14. Such a hardening ofthe sealant bead 14 is desirable in that the hardened sealant bead 14 iseasily removable with little or no residue from both the forming tool 16and the fluoroelastomeric strip 24 by rolling the tape back onto itself.The vulcanized sealant bead 14 is not reusable and is discarded. Incomparison, a sealant bead 14 that is not vulcanizing would retain itspre-autoclave, gummy consistency making removal from the sealing surfacedifficult and time-consuming.

[0031] Advantageously, fluoroelastomeric material has strength and tearresistance that is compatible for use with an elastomeric layer 20formed of silicone rubber. Furthermore, the semi-rigid nature of thefluoroelastomeric material enhances its conformability to forming tools16 having complex curved surfaces with small inside or outside radii.Notably, as was mentioned above, it has been found that Mosites #10320-C, manufactured by the Mosites Rubber Company of Fort Worth, Tex.is a preferred material that may be utilized for forming thefluoroelastomeric strip 24. In contrast to prior art reusable vacuumbags wherein the sealant tape is applied directly to a silicone rubberelastomeric layer 20 at the sealing flange 22 with poor adhesiontherebetween, in the present invention, the sealant bead is applied tothe fluoroelastomeric strip. It has been found that the preferredfluoroelastomeric material, Mosites #10320-C, has a fluorine content of70%. The high fluorine content in Mosites #10320-C provides a highdegree of chemical inertness and resistance to degradation that mayotherwise occur during exposure to volatiles created during theautoclaving process. Without resistance to attack from volatiles,tacifiers and acids, the mechanical properties of the sealing flange 22would degrade after two or three autoclave cycles to a degree such thatthe vacuum bag would not be reusable.

[0032] As shown in FIG. 3, the first surface 26 of the fluoroelastomericstrip 24 is bonded to the sealing flange 22. The second surface 28 ofthe fluoroelastomeric strip 24 is releaseably adhered to the sealantbead 14. It is contemplated that at least one layer of a release agent30 may be disposed between the sealant bead 14 and the second surface 28of the fluoroelastomeric strip 24 to prevent permanent bondingtherebetween during autoclaving. The fluoroelastomeric strip 24 may beformed of fluorinated synthetic rubber, which may be uncuredfluoroelastomeric rubber. The fluoroelastomeric strip 24 may be formedof a material having a fluorine content of at least 70%. As waspreviously mentioned, Mosites #10320-C is a preferred fluoroelastomericmaterial that will form a permanent bond with an elastomeric layer 20formed of silicone rubber.

[0033] Referring to FIG. 5, the method of fabricating the reusablevacuum bag 10 will now be discussed. FIG. 5 is a broken away perspectiveview illustrating the forming tool 16 and the reusable vacuum bag 10during its fabrication thereon. As can be seen in FIG. 5 the formingtool 16 used in fabricating the reusable vacuum bag 10 is identical tothe forming tool 16 of FIG. 1 which is used to form the composite part18. As was mentioned above, the reusable vacuum bag 10 may be formed ofat least one elastomeric layer 20, although multiple elastomeric layers20 may make up the reusable vacuum bag 10. The elastomeric layer 20 maybe formed of cured or uncured silicone rubber and may have a thicknessof from about 0.030 inches to about 0.120 inches, although the thicknessof the silicone rubber may be variable at different sections of thereusable vacuum bag 10.

[0034] The reusable vacuum bag 10 is fabricated by providing theelastomeric layer 20 with the sealing flange 22 extending about itsperiphery. The fluoroelastomeric strip 24 may be formed of fluorinatedsynthetic rubber, which may be uncured fluoroelastomeric rubber.Additionally, the uncured fluoroelastomeric rubber may contain aperoxide curative for initiating vulcanization with the silicone rubber.As mentioned above, Mosites #10320-C is the preferred fluoroelastomericmaterial that will bond with the elastomeric layer 20 formed of siliconerubber due in part to its peroxide curative content. Furthermore,Mosites #10320-C adheres to commercially available sealant tapes such aszinc chromate sealant tape while being chemically resistant to attackfrom tacifiers that may contact the fluoroelastomeric strip 24 duringautoclaving. The chemical resistance of Mosites #10320-C is due in partto its hitch fluorine content of 70%.

[0035] Referring now to FIG. 6, shown is an enlarged partiallongitudinal sectional view taken along line 6-6 of FIG. 5 illustratingthe detail of the sealing flange 2′ during fabrication of the reusablevacuum bag 10. The forming tool 16 is covered with the elastomeric layer20 such that the sealing flange 22 extends beyond the forming tool 16perimeter to facilitate sealing of the reusable vacuum bag 10 to theforming tool 16. As can be seen in FIG. 6, the forming tool 16 may beoverlaid with a model part 40 prior to covering with the elastomericlayer 20. Such a model part 40 would be preformed and would have thesame thickness and geometric features of the composite part 18 which isto be ultimately molded on the forming tool 16. However, the use of themodel part 40 depends to some degree on the thickness of the laminates.If the laminate thickness is small and the lateral geometric featuresare not too large, the model part 40 need not be incorporated into theprocess for fabricating the reusable vacuum bag 10. The reusable vacuumbag 10 may be overlaid directly on the forming tool 16.

[0036] Turning back to the description of the process for fabricatingthe reusable vacuum bag 10, the fluoroelastomeric strip 24 is providedhaving a shape substantially matching that of the sealing flange 22. Thefluoroelastomeric strip 24 is then positioned between the sealing flange22 and the forming tool 16 such that the fluoroelastomeric strip 24 issubstantially aligned along the sealing flange 22. A nylon bag 38 isprovided for vacuum bagging. The combination of the forming tool 16 andthe overlaying reusable vacuum bag 10 is then vacuum bagged with thenylon bag 38 using conventional bagging techniques. The reusable vacuumbag 10 is then cured in an autoclave or oven at elevated temperature andpressure. After curing, the nylon bag 38 and the reusable vacuum bag 10are removed from the forming tool 16. The nylon bag 38 is discarded andthe reusable vacuum bag 10 is stabilized by postcuring in an oven atambient pressure and elevated temperature greater than the curingtemperature. The elevated temperature during stabilization is set to behigher than any temperature to which the reusable vacuum bag 10 will besubjected during future debulking and autoclaving operations. Theelevated temperature used during the postcuring step may be about 500higher than that used in the autoclaving step. The stabilization stepminimizes further shrinkage of the reusable vacuum bag 10 and stabilizesthe shape of the reusable vacuum bag 10. In order to improve the sealbetween the sealant bead 14 and the fluoroelastomeric strip 24, thesecond surface 28 may be lightly hand-abraded with 120-grit sandpaper byrubbing the second surface 28 for no more than one minute such that anysheen of the second surface 28 may be slightly dulled. In order tofurther improve the ease with which the sealant bead 14 may be removedfrom the fluoroelastomeric strip 24, the release agent 30 may be appliedto the fluoroelastomeric strip 24 after the stabilization step.

[0037] Additional modifications and improvements of the presentinvention may also be apparent to those of ordinary skill in the art.Thus, the particular combination of parts described and illustratedherein is intended to represent only certain embodiments of the presentinvention, and is not intended to serve as limitations of alternativedevices within the spirit and scope of the invention.

What is claimed is:
 1. A reusable vacuum bag configured for applicationof at least one sealant bead, the sealant bead providing vacuum tightsealing of the reusable vacuum bag to a forming tool during fabricationof a composite part on the forming tool, the reusable vacuum bagcomprising: at least one elastomeric layer having polymers, theelastomeric layer being sealable to the forming tool and having asealing flange extending peripherally thereabout; and afluoroelastomeric strip having polymers and extending substantiallyalong the sealing flange and having first and second surfaces, thepolymers of the elastomeric layer cross-linking with the polymers of thefluoroelastomeric strip at an elevated temperature such that a permanentbond is formed between the sealing flange and the fluoroelastomericstrip at the first surface, the fluoroelastomeric strip beingreleaseably adhered at the second surface to the sealant bead.
 2. Thereusable vacuum bag of claim 1 wherein the elastomeric layer and thefluoroelastomeric strip both include a peroxide curative, the peroxidecurative initiating vulcanization of the fluoroelastomeric strip to thesealing flange at an elevated temperature such that a permanent bond isformed therebetween.
 3. The reusable vacuum bag of claim 2 wherein thevulcanization of the fluoroelastomeric strip to the sealing flange formsdouble-oxygen bonds therebetween.
 4. The reusable vacuum bag of claim 1wherein the sealant tape includes tacifiers therein for providingadhesion between the sealant bead and the fluoroelastomeric strip. 5.The reusable vacuum bag of claim 1 wherein the fluoroelastomeric stripis formed of a material having a fluorine content of at least 70%. 6.The reusable vacuum bat of claim 1 wherein the fluoroelastomeric stripis conformable to the forming tool.
 7. The reusable vacuum bag of claim1 wherein the fluoroelastomeric strip is formed of fluorinated syntheticrubber.
 8. The reusable vacuum bag of claim 1 wherein thefluoroelastomeric strip is uncured fluoroelastomeric rubber.
 9. Thereusable vacuum bag of claim 1 wherein the elastomeric layer is siliconerubber.
 10. The reusable vacuum bag of claim 1 wherein the elastomericlayer is uncured silicone rubber.
 11. The reusable vacuum bag of claim 1wherein the sealant bead is formed of zinc chromate sealant tape. 12.The reusable vacuum bag of claim 1 wherein the width of the sealingflange is in a range of from about ½ inch to about 3 inches.
 13. Thereusable vacuum bag of claim 1 wherein the elastomeric layer has athickness of from about 0.030 inches to about 0.120 inches.
 14. A methodof fabricating a reusable vacuum bag configured for application of atleast one sealant bead, the sealant bead providing vacuum tight sealingof the reusable vacuum bag to a forming tool during fabrication of acomposite part formed on the forming tool, the method comprising thesteps of: providing an elastomeric layer having a sealing flangeextending peripherally thereabout; covering the forming tool with theelastomeric layer such that the sealing flange extends beyond theforming tool perimeter; providing a fluoroelastomeric strip having ashape substantially matching that of the sealing flange; positioning thefluoroelastomeric strip between the sealing flange and the forming toolsuch that the fluoroelastomeric strip is substantially aligned along thesealing flange; providing a nylon bag for vacuum bagging the reusablevacuum bag; curing the reusable vacuum bag against the forming tool atelevated temperature and pressure; removing the reusable vacuum bag fromthe nylon bag; and stabilizing the reusable vacuum bag against furthershrinkage by postcuring in an oven at an elevated temperature greaterthan the curing temperature.
 15. The method of claim 15 furtherincluding the step of applying a release agent to the fluoroelastomericstrip.
 16. The method of claim 15 further including the step of coveringthe forming tool with a model part and wherein the model part is coveredby the elastomeric layer.
 17. The method of claim 15 wherein thepostcuring step is carried out in an oven at ambient pressure.
 18. Themethod of claim 15 wherein the postcuring step is carried out in an ovenat a temperature of about 50° higher than that used in the curing step.19. The method of claim 15 wherein the elastomeric layer is uncuredsilicone rubber.
 20. The method of claim 15 wherein thefluoroelastomeric strip is uncured fluoroelastomeric rubber containing aperoxide curative.
 21. The reusable vacuum bag of claim 15 wherein thefluoroelastomeric strip is formed of a material having a fluorinecontent of at least about 70%.